Which relay do I need?

Question

I think I need a SPST 12 V, 30 A latching relay.

I would like to fit the circuit to my van for a machine which cannot be run whilst the vehicle is in motion. Therefore I will use a micro switch with the clutch pedal, therefore when the clutch pedal is pressed the machine does not work. I will be wiring the micro switch output to the relay (coil side), then put a negative to the other side of the coil. Then I will have a common from the battery to the relay. Then I will have the output of the relay to the machines on/off switch.

Now my problem is that I would also like a momentary switch in this circuit somewhere, so that even if the clutch is not pressed the machine is not on. I can't use the normal machine off switch as it is too far in the back of the van. Where would I put this switch and which exact relay do I need for this setup?

Answer 1

perhaps something like this:

^{simulate this circuit – Schematic created using CircuitLab} improved version:

^{simulate this circuit}

The relay is just an ordinary automotive headlamp/horn relay the 30A fuse prevents damage to the cable to the machine from starting a fire and the 1A fuses do the same for the control circuit (allowing the use of smaller wire for those circuits)

pressing the stop button or the clutch cuts the power to the relay turning it off.

pressing the start button feeds power to the relay turning it on and then the relay feeds power to itself after that.

the 1A fuses can be 3AG fuses in in-line fuse-holders the 30A should probably be an automotive blade fuse in a suitable fuse block.

lever of the clutch pedal may suffice.

^{simulate this circuit}

finally here's a simplified version. the start buttone will need to be a heavy duty type capable of running the machine.

the switch on the clutc need to be heavy duty, and as it is a switch to ground a simple contact that contacts the